Preclinical cost analysis of orthopaedic implants: a custom versus standard cementless femoral component for revision total hip arthroplasty

A preclinical cost analysis method was introduced to assess the cost effectiveness of using a custom implant instead of standard “off-the-shelf” implants for revision total hip arthroplasty. Finite element models of proximal femur–implant systems were constructed and an array of environmental factors, including loads and bone properties, was incorporated into a computer experiment to evaluate relative motion between implant and bone. Implant performance related cost was then determined from relative motion measures using a quality loss function. Unit manufacturing cost was added to implant performance cost to determine the cost difference between the two implants. The reduction in relative motion achieved by the custom implant with respect to an equivalent-lengthed standard implant justified its additional unit manufacturing costs. In response to these results and suggestions by surgeons, we increased the length of the standard implant by 50mm and performed an identical series of analyses. We found that increasing the stem length to 120mm substantially decreased the relative motion of the standard implant to values less than for the custom implant. This case study provides preliminary evidence that a surgical inventory consisting of longer-stemmed standard implants or modular distal stems is more cost effective than designing custom devices on a case-by-case basis. Additional design studies are warranted before generalizing such a claim.